This invention relates to expansion hoses and, more particularly, to a new and improved expansion hose especially adapted to inhibit hydraulic pressure pulsations.
Expansion hoses designed to reduce pulsations in hydraulic pressure are used in hydraulic circuits such as those in the power steering mechanism of an automobile. In order to reduce pressure pulsations caused by hydraulic pumps, and the humming noises connected therewith, conventional expansion hoses are composed of a material which is expandable within certain limits so that, upon increase of the working pressure of the pressure medium flowing through the hose, the hose wall can expand correspondingly. Thus, corresponding variations in the interior volume of the hose will occur as a function of the prevailing working pressure so that pressure pulsations at the outlet and the expansion hose are noticeably smaller than the pulsations at the inlet side of the expansion hose.
The extent of the pulsation reduction depends, among other things, upon the internal volume of the hose, i.e. its cross section and length, as well as the expandability of the hose material. In view of the conventional working pressures, on the one hand, and the space available to accommodate the expansion hose, on the other hand, however, the cross section and length of the hose must be limited.
In order to achieve an improved pulsation reduction in spite of these limitations, an expansion hose has been provided with a throttle element approximately at the center of the hose, the throttle element having an axial throttle passage so that the hose interior is divided into two hose chambers connected with each other by the throttle passage.
It is also known to provide an inner hose having radial throttle passages in the interior of the expansion hose in place of a throttle element, one end of the inner hose being connected with the hose inlet to reduce pulsations, the other end opening freely into the interior of the expansion hose. Thus, the hydraulic fluid flows by way of the inner hose into the interior of the expansion hose so that part of the hydraulic fluid emerges through the radial passages of the inner hose and another part flows through to the end of the inner hose. As with the use of the center throttle element, the use of an inner hose results in some reduction of the pressure pulsation.
In many cases, such as in power steering mechanisms of automobiles, such an expansion hose is inserted as a connecting line between the hydraulic pump and the power steering gear. Nevertheless the pressure pulsation, even though decreased by the use of expansion hoses modified in this manner, still causes reduced riding comfort.
Accordingly, it is an object of the present invention to provide an improved expansion hose which effectively overcomes the disadvantages of the prior art.
Another object of the invention is to provide an expansion hose by which a clearly perceptible reduction of the pressure pulsation is effected without the need to increase the overall hose dimensions or the internal hose volume.